Image coded data re-encoding apparatus

ABSTRACT

An image coded data re-encoding apparatus ( 30 ) which generates in an image coded data analyzer ( 310 ) coded data after signal processing ( 221 ) by performing a first digital signal processing on first image coded data ( 220 ), supplies an image coded data synthesizer ( 320 ) with the coded data after signal processing ( 221 ) and multiple signals ( 222 ) associated with the first image coded data, and generates in the image coded data synthesizer ( 320 ) a second image coded data ( 240 ) by performing on the coded data after signal processing ( 221 ) a second digital signal processing based on multiple signals ( 222 ). The second image coded data is generated without once decoding the first image coded data. This makes it possible to prevent degradation in image quality, delay involved in the transform and an increase of the device size.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an image coded data re-encodingapparatus for producing a second image coded data by applying digitalsignal processing to a first image coded data which is obtained bycoding a digital input image signal.

[0003] 2. Description of Related Art

[0004]FIG. 16 is a block diagram showing a conventional image coded datare-encoding apparatus disclosed in Japanese patent application laid-openNo. 2-179186/1990, for example. It is an example of a multiple sitevideo conference system. In this figure, the reference numeral 1designates a master station, 2 designates a relay station, 3 designatesa slave station, 10 designates an image coder of the stations, and 20designates an image decoder. The reference numerals 101 designates aninput image, 102 designates image coded data, 103 designates a decodedimage signal, 104 designates image re-encoded data, and 105 designates adecoded image signal. The operation will now be described.

[0005] The image coder 10 of the master station 1 performs coding of theinput image 101, and sends the image coded data 102 to the relay station2. The relay station 2 receives the image coded data 102 with its imagedecoder 20 to decode it, and generates the image re-encoded data 104 byre-encoding the decoded image signal 103 with the image coder 10. Theimage re-encoded data 104 thus generated by the re-encoding istransmitted to the slave station 3. The slave station 3 decodes with theimage decoder 20 the image re-encoded data 104 which is relayed throughthe relay station 2, and uses it as the decoded image signal 105.

[0006] When holding a conference using the relay station 2 with such adecoding and relaying function, it often occurs that the master station1 and the slave station 3 employ different coding systems. In this case,it becomes necessary to change the amount of coded data to be generatedand various types of parameters such as image size and a frame rate.Thus, the relay station 2 once decodes the received image coded data 102into the decoded image signal 103, and then re-encodes it into the imagere-encoded data 104, thereby matching the different coding systems.

[0007] In this way, the conventional image coded data re-encodingapparatus has a process through which the image coded data is oncedecoded image to be re-encoded to achieve relaying or copying of theimage coded data.

[0008] Since the conventional image coded data re-encoding apparatuswith such an arrangement once decodes the image coded data 102 into thedecoded image signal 103, and then re-encodes the decoded image signal103 regardless of its contents to relay or convert the image coded data102, it has some problems such as degrading the image quality of thedecoded image signal 105, increasing a delay involved in the relay andtransform, and augmenting the size of the apparatus.

SUMMARY OF THE INVENTION

[0009] The present invention is accomplished to solve such problems, andto provide an image coded data re-encoding apparatus which can reducethe image degradation, shorten the processing delay, and shrink thedevice size, thereby achieving an efficient transform of the image codeddata.

[0010] According to one aspect of the present invention, there isprovided an image coded data re-encoding apparatus comprising: an imagecoded data analyzer for generating coded data after signal processing byperforming a first digital signal processing on a first image codeddata; and an image coded data synthesizer for generating a second imagecoded data by performing on the coded data after signal processing asecond digital signal processing based on multiple signals associatedwith a first image coded data by using the coded data after signalprocessing output from the image coded data analyzer and the multiplesignals.

[0011] This will offer an advantage of reducing the degradation of theimage quality after the transform, decreasing processing delay, andachieving an image coded data re-encoding apparatus with a reduced sizein comparison with a system in which the first image coded data isalways once decoded into a decoded image, followed by re-encoding of thedecoded image into the second image coded data regardless of the decodeddata.

[0012] In image coded data re-encoding apparatus, the image coded dataanalyzer may extract the multiple signals in the course of generatingthe coded data after signal processing by performing the first digitalsignal processing on the first image coded data, and may provides theimage coded data synthesizer with the coded data after signalprocessing.

[0013] This will offer an advantage of providing an informationeffective image coded data re-encoding apparatus capable of obviatingspecial additional information which was needed for the second digitalsignal processing for generating the second image coded data.

[0014] In the image coded data re-encoding apparatus, the image codeddata re-encoding apparatus may further comprise a separator forseparating from the first image coded data the multiple signals whichhave been externally combined with the first image coded data and cannotbe extracted from the first image coded data in the first digital signalprocessing for generating the coded data after signal processing, andthe image coded data synthesizer may generate the second image codeddata by using the multiple signals output from the separator.

[0015] This will offer an advantage of providing a coded datare-encoding apparatus which can use, in the second digital signalprocessing for generating the second image coded data, information whichcannot be extracted in course of the first digital signal processing,and this will make possible more effective transform than when suchinformation is not used.

[0016] The image coded data re-encoding apparatus may further comprisean information extractor/estimator for extracting or estimating themultiple signals needed for the second digital signal processing fromthe coded data after signal processing generated by the image coded dataanalyzer, and the image coded data synthesizer may generate the secondimage coded data by using the multiple signals output from theinformation extractor/estimator.

[0017] This will offer an advantage of providing an image coded datare-encoding apparatus with a simple configuration because it obviatesspecial processing involved in decoding.

[0018] In the image coded data re-encoding apparatus, the image codeddata synthesizer may generate the second image coded data with a dataamount different from a data amount of the first image coded data inputto the image coded data analyzer.

[0019] This will offer an advantage of providing an image coded datare-encoding apparatus which can perform transformation between data ofdifferent amounts with reduced image degradation and processing delay.

[0020] The image coded data re-encoding apparatus may further comprise acoefficient deletion/addition/correction portion for deleting part ofthe transform coefficients or quantization indices, which are extractedby the image coded data analyzer, and for correcting the transformcoefficients or quantization indices in accordance with a ratio ofamounts of data to be transformed.

[0021] This will offer an advantage that the amount of data can bereduced because part of the transform coefficients or the quantizationindices is deleted, and that the image quality of the decoded image canbe improved as compared with a system which simply thins out thetransform coefficients or quantization indices because the remainder ofthe transform coefficients or the quantization indices is corrected inaccordance with the ratio of amounts of data to be transformed.

[0022] The image coded data re-encoding apparatus may further comprise acoefficient deletion/addition/correction portion for deleting part ofthe transform coefficients or quantization indices, which are extractedby the image coded data analyzer, and are weighted in accordance withrelationships between the transform coefficients or quantization indicesand their neighboring transform coefficients or quantization indices.

[0023] This will offer an advantage that the amount of data can bereduced, and the image quality of the decoded image can be improved ascompared with a system which simply thins out the transform coefficientsor quantization indices.

[0024] The image coded data re-encoding apparatus may further comprise acoefficient deletion/addition/correction portion for adding, to thetransform coefficients or quantization indices which are extracted inthe image coded data analyzer, new transform coefficients orquantization indices after correcting the new transform coefficients orquantization indices in accordance with a ratio of amounts of data to betransformed.

[0025] This will offer an advantage of achieving transform with improvedimage quality as compared with a system which simply adds the transformcoefficients or quantization indices because the newly added transformcoefficients or quantization indices are corrected in accordance withthe ratio of amounts of data to be transformed, and hence the dataamount of the additional data can be adjusted considering the imagequality after inverse transform.

[0026] The image coded data re-encoding apparatus may further comprise acoefficient deletion/addition/correction portion for adding, to thetransform coefficients or quantization indices which are extracted inthe image coded data analyzer, new transform coefficients orquantization indices after predicting transform coefficients orquantization indices including the new transform coefficients orquantization indices and their neighboring transform coefficients orquantization indices.

[0027] This will offer an advantage of achieving transform with improvedimage quality, providing clearer images than a system which simply addsthe transform coefficients or quantization indices, because suchprediction is carried out as improving the decoded image quality inadding the transform coefficients or quantization indices.

[0028] The image coded data re-encoding apparatus may further comprise acoefficient deletion/addition/correction portion for increasing a ratioof deletion of the transform coefficients or quantization indices, whichare extracted by the image coded data analyzer, if the coding parameterdesignating the picture type indicates, when decision is made whether ornot the current image to be processed is used for prediction in futurecoding, that the picture type is not used for the prediction in thefuture coding.

[0029] This will offer an advantage of achieving high quality transformwhich can maintain the total image quality on the time axis because whena frame of unit time length is not used for the coding in the next unittime, only the data amount associated with the frame can be reduced.

[0030] The image coded data re-encoding apparatus may further comprise acoefficient deletion/addition/correction portion for decreasing a ratioof deletion of the transform coefficients or quantization indices, whichare extracted by the image coded data analyzer, if the coding parameterdesignating the picture type indicates, when decision is made whether ornot the current image to be processed is used for prediction in futurecoding, that the picture type is used for the prediction in the futurecoding.

[0031] This will offer an advantage of achieving high quality transformwhich can maintain the total image quality on the time axis because whena frame of unit time length is used for the coding in the next unittime, the reduction ratio of the data in the frame is decreased.

[0032] The image coded data re-encoding apparatus may further comprise acoefficient deletion/addition/correction portion for increasing a ratioof deletion of the transform coefficients or quantization indices, whichare extracted by the image coded data analyzer, if the coding parameterdesignating the predictive type of the image block indicates, whendecision is made whether a current image to be processed is used forprediction in future coding by using the coding parameters generated bythe image coded data analyzer, that the image block is not used for theprediction in the future coding, even if the coding parameterdesignating the picture type indicates that the picture type is used forthe prediction in the future coding.

[0033] This will offer an advantage of achieving transform with improvedimage quality on the time axis because the decision is made of anincrease of the deletion ratio of the transform coefficients or thequantization indices by using the coded block information in addition tothe coded picture information, and hence finer control becomes possible.

[0034] In the image coded data re-encoding apparatus, the image codeddata synthesizer may generate the second image coded data whose decodingprocedure differs from a decoding procedure of the first image codeddata input to the image coded data analyzer.

[0035] This will offer an advantage of providing higher quality imageafter the transform when generating image coded data between differentcoding systems.

[0036] The image coded data re-encoding apparatus may further comprise acoding parameter corrector/transformer for correcting and transformingthe expression form of various types of coding parameters, which areextracted by the image coded data analyzer, from the expression form inthe decoding procedure of the first image coded data to an expressionform in the decoding procedure of the second image coded data.

[0037] This will offer an advantage of providing a small size,inexpensive apparatus because it becomes unnecessary for the first imagecoded data to be once decoded into an image and then re-encoded inaccordance with the coding system, even when the first image coded datainput to the image coded data analyzer has different coding system fromthe second coded data output from the image coded data synthesizer.

[0038] In the image coded data re-encoding apparatus, the image codeddata synthesizer may generate the second image coded data including animage signal whose image size differs in time or space from an imagesize of an image signal included in the first image coded data input tothe image coded data analyzer.

[0039] This will offer an advantage of providing an image coded datare-encoding apparatus which facilitates the transform between thedifferent image sizes in time or space, thereby achieving high qualityimage after the transform.

[0040] The image coded data re-encoding apparatus, may further comprisea coefficient deletion/addition/correction portion for changing anamount of the transform coefficients or quantization indices extractedby the image coded data analyzer, and for correcting the transformcoefficients or quantization indices, which are extracted by the imagecoded data analyzer, in accordance with a ratio of the image sizes to betransformed.

[0041] This will offer an advantage of reducing the degradation of theimage quality after the change in the image size by suppressing sharpdegradation in the resolution or unnaturalness of the image, because thetransform coefficients or the quantization indices are corrected inaccordance with the image sizes to be varied in the coded data transforminvolving the image size change.

[0042] The image coded data re-encoding apparatus may further comprise acoefficient deletion/addition/correction portion for correctingdimension of the motion vectors extracted by the image coded dataanalyzer in accordance with a ratio of the image sizes to betransformed.

[0043] This will offer an advantage that a characteristic is obtained,which substantially matches the characteristic obtained in a widermotion compensative search range, by a narrower range motioncompensative search, because of the improved motion compensationefficiency in the image coded data after the transform since thedimension of the motion vectors are corrected in accordance with theratio of the image sizes to be changed.

[0044] In the image coded data re-encoding apparatus, the image codeddata synthesizer may generates the second image coded data including animage signal whose sequence differs from a sequence of an image signalincluded in the first image coded data input to the image coded dataanalyzer.

[0045] This will offer an advantage of providing an image coded datare-encoding apparatus that can achieve transform between image codeddata whose image signal sequences are different, thereby achieving highimage quality after the transform.

[0046] The image coded data re-encoding apparatus may further comprise amotion searcher for estimating dimension of the motion vectors extractedby the image coded data analyzer in accordance with the sequence of theimage signals to be transformed.

[0047] This will offer an advantage of improving the efficiency ofcoding using the motion vectors after the transform by estimating thedimension of the motion vectors in accordance with the sequences of theimages to be transformed.

[0048] In the image coded data re-encoding apparatus, the image codeddata synthesizer may generate the second image coded data whose decodedimage signal includes a number of frames per unit time different from anumber of frames per unit time of a decoded image signal of the firstimage coded data input to the image coded data analyzer.

[0049] This will offer an advantage of providing an image coded datare-encoding apparatus capable of implementing the transform into theimage coded data whose number of image frames differs from that of thedecoded image signal, thereby achieving high image quality after thetransform.

[0050] The image coded data re-encoding apparatus may further comprise aquantization estimator for estimating, from the decoded image outputfrom the image coded data analyzer, quantization parameters obtained inthe course of generating the first image coded data, and the image codeddata synthesizer may generate the second image coded data by using thequantization parameters estimated by the quantization estimator.

[0051] This is effective when the image coded data analyzer carries outoperation matching a common decoding operation, and will offer anadvantage of providing an image coded data re-encoding apparatus capableof maintaining the image quality after the transform in such applicationas relay transmission because the estimation of the quantization indicesfrom the decoded image makes it possible to improve the image quality ofthe second image coded data. In addition, it offers an advantage ofimplementing an optimum transform by controlling the quantizationparameters in accordance with the ratio of data rates before and afterthe transform. In particular, the best image quality can be achievedwhen the rates are identical before and after the transform.

BRIEF DESCRIPTION OF THE DRAWINGS

[0052]FIG. 1 is a block diagram showing a first embodiment of an imagecoded data re-encoding apparatus in accordance with the presentinvention;

[0053]FIG. 2 is a block diagram showing a coding processor in the firstembodiment;

[0054]FIG. 3 is a schematic diagram illustrating a coding mode in thecoding processor;

[0055]FIG. 4 is a block diagram showing a decoding processor in thefirst embodiment;

[0056]FIG. 5 is a block diagram showing a second embodiment of an imagecoded data re-encoding apparatus in accordance with the presentinvention;

[0057]FIG. 6 is a block diagram showing a third embodiment of an imagecoded data re-encoding apparatus in accordance with the presentinvention;

[0058]FIG. 7 is a block diagram showing fourth to seventh embodiments ofan image coded data re-encoding apparatus in accordance with the presentinvention;

[0059]FIG. 8 is a block diagram showing eighth and ninth embodiments ofan image coded data re-encoding apparatus in accordance with the presentinvention;

[0060]FIG. 9 is a block diagram showing a tenth embodiment of an imagecoded data re-encoding apparatus in accordance with the presentinvention;

[0061]FIG. 10 is a block diagram showing an eleventh embodiment of animage coded data re-encoding apparatus in accordance with the presentinvention;

[0062]FIG. 11 is a block diagram showing a twelfth embodiment of animage coded data re-encoding apparatus in accordance with the presentinvention;

[0063]FIG. 12 is a block diagram showing a thirteenth embodiment of animage coded data re-encoding apparatus in accordance with the presentinvention;

[0064]FIG. 13 is a block diagram showing a fourteenth embodiment of animage coded data re-encoding apparatus in accordance with the presentinvention;

[0065]FIG. 14 is a block diagram showing a fifteenth embodiment of animage coded data re-encoding apparatus in accordance with the presentinvention;

[0066]FIG. 15 is a block diagram showing a sixteenth embodiment of animage coded data re-encoding apparatus in accordance with the presentinvention; and

[0067]FIG. 16 is a block diagram showing a conventional image coded datare-encoding apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0068] The invention will now be described with reference to theaccompanying drawings.

[0069] Embodiment 1

[0070]FIG. 1 is a block diagram showing a first embodiment of an imagecoded data re-encoding apparatus in accordance with the presentinvention, together with a coding processor and a decoding processor,wherein the coding processor codes an input image signal to be subjectedto the digital signal processing in the image coded data re-encodingapparatus, and the decoding processor decodes the image coded dataprocessed in the image coded data re-encoding apparatus. In this figure,the reference numeral 30 designates an image coded data re-encodingapparatus, 40 designates a coding processor, and 50 designates adecoding processor. The reference numeral 200 designates a digital inputimage signal supplied to the coding processor 40, 220 designates a firstimage coded data obtained by coding the input image signal 200 by thecoding processor 40, 240 designates a second image coded data obtainedby applying digital signal processing to the first image coded data 220in the image coded data re-encoding apparatus 30, and 250 designates adecoded image signal obtained by decoding the second image coded data240 in the decoding processor 50.

[0071] In the image coded data re-encoding apparatus 30, the referencenumeral 310 designates an image coded data analyzer, and 320 designatesan image coded data synthesizer. The image coded data analyzer 310performs a first digital signal processing on the first image coded data220 fed from the coding processor 40. The image coded data synthesizer320 receives the coded data after the signal processing output from theimage coded data analyzer 310 together with multiple signals associatedwith the first image coded data, and performs a second digital signalprocessing on the coded data after the signal processing on the basis ofthe multiple signals, thereby generating a second image coded data 240.The reference numeral 221 designates the coded data after signalprocessing, which is transferred from the image coded data analyzer 310to the image coded data synthesizer 320, and 222 designates the multiplesignals associated with the first image coded data 220, which are alsotransferred from the image coded data analyzer 310 to the image codeddata synthesizer 320. The reference numeral 223 designates informationfor instructing a data amount and an image size to be transformed, whichis input to the image coded data synthesizer 320.

[0072] In the coding processor 40, the reference numeral 401 designatesa transformer, 402 designates a quantizer, and 403 designates a variablelength coder. The transformer 401 carries out operations such asdiscrete cosine transform (called DCT below) to generate transformcoefficients from the input image signal 200. The quantizer 402generates quantization indices by applying a scalar quantizationprocessing to the transform coefficients generated by the transformer401. The variable length coder 403 performs variable length coding onthe quantization indices generated by the quantizer 402 by using Huffmancodes or the like.

[0073] In the decoding processor 50, the reference numeral 501designates a variable length decoder, 502 designates an inversequantizer, and 503 designates an inverse transformer. The variablelength decoder 501 applies the variable length decoding to the secondimage coded data 240. The inverse quantizer 502 performs inverse scalarquantization processing on the quantization indices decoded by thevariable length decoder 501. The inverse transformer 503 performs theinverse DCT on the transform coefficients generated by the inversequantization by the inverse quantizer 502 to obtain the decoded imagesignal 250. In the coding processor 40 and decoding processor 50, onlyblocks are shown for implementing basic functions.

[0074] Next, the operation will be described.

[0075] The digital input image signal 200 is input to the codingprocessor 40 comprising the transformer 401, quantizer 402 and variablelength coder 403 to be coded into the first image coded data 220. Theoperation of the coding processor 40 will be described below.

[0076]FIG. 2 is a block diagram showing a concrete configuration of thecoding processor 40 to describe its operation. It includes thetransformer 401, quantizer 402 and variable length coder 403 forimplementing the basic function for coding the input image signal 200into the first image coded data 220, together with an additional portionfor implementing a motion compensative prediction. In this figure, thereference numeral 404 designates a current coded data frame memory forstoring the input image signal 200, and 405 designates a subtracter forsubtracting a predicted frame image 210 from a current frame image 201read out of the current coded data frame memory 404, thereby generatinga prediction error frame image 202. The predicted frame image 210 is fedfrom a motion compensative predictor which will be described later. Thereference numeral 203 designates the transform coefficients output fromthe transformer 401 as a result of the DCT of the prediction error frameimage 202 by the transformer 401. The reference numerals 204 and 205designate the quantization indices and quantization parameters,respectively, which are generated by the scalar quantization of thetransform coefficients 203 by the quantizer 402 and supplied to thevariable length coder 403. The reference numeral 406 designates aninverse quantizer for carrying out the inverse quantization of thequantization indices 204 output from the quantizer 402, 407 designatesan inverse transformer for performing inverse transform (inverse DCT) ontransform coefficients 206 which is obtained by the inverse quantizationby the inverse quantizer 406, and 408 designates an adder for adding alocal prediction error frame image 207, which is generated by theinverse transform by the inverse transformer 407, to the predicted frameimage 210 from the motion compensative predictor. The reference numeral409 designates a preceding coded data frame memory for storing a localdecoded frame image 208 obtained as a result of addition by the adder408, and 410 designates a motion compensative predictor for generating apredicted frame image 210 delivered to the subtracter 405 and the adder408, and motion vectors 211 supplied to the variable length coder 403,on the basis of a preceding frame image 209 read out of the precedingcoded data frame memory 409 and the current frame image 201 read out ofthe current coded data frame memory 404. The variable length coder 403generates the first image coded data 220 using the motion vectors 211,the quantization parameters 205 from the quantizer 402, and thequantization indices 204 from the quantizer 402.

[0077] The coding processor 40 with the configuration as shown in FIG. 2operates as follows in accordance with the MPEG 1 (Moving Picture ExpertGroup 1) standard proposed by the joint conference of ISO (InternationalOrganization for Standardization) and IEC (InternationalElectrotechnical Commission). First, the digital input image signal 200is stored in the current coded data frame memory 404, and the currentframe image 201 to be coded which is read out of the current coded dataframe memory 404 is input to the subtracter 405. The subtracter 405subtracts from the input signal the predicted frame image 210 fed fromthe motion compensative predictor 410, thereby generating the predictionerror frame image 202. Subsequently, the transformer 401 transforms theprediction error frame image 202 using the DCT to generate the transformcoefficients 203. The quantizer 402 performs the scalar quantizationprocessing in accordance with quantization steps using feedback controlwhich monitors the amount of generated codes with reference to thetransform coefficients 203 to keep that amount constant, or using feedforward control based on the detected variance of the input image signal200, thereby generating the quantization indices 204. The variablelength coder 403 performs the variable length coding on the quantizationindices 204 using the Huffman codes together with the quantizationparameters 205 generated by the quantizer 402 and the motion vectors 211generated by the motion compensative predictor 410, thus generating thefirst image coded data 220. The first image coded data 220 istransmitted through a communication channel, or stored in a storagemedium such as CD ROM (compact disk memory) or video tape.

[0078] The inverse quantizer 406 performs inverse quantization of thequantization indices 204 generated by the quantizer 402, and outputs thetransform coefficients 206. The inverse transformer 407 carries out onthe transform coefficients 206 the inverse transform using the inverseDCT to generate the local prediction error frame image 207 fed to theadder 408. The adder 408 adds the local prediction error frame image 207to the predicted frame image 210 fed from the motion compensativepredictor 410 to generate the local decoded frame image 208 which isstored in the preceding coded data frame memory 409. Subsequently, themotion compensative predictor 410 performs pattern matching of the codedpreceding frame image 209 read out of the preceding coded data framememory 409 with the current frame image 201 read out of the currentcoded data frame memory 404 to generate the motion compensated predictedframe image 210 which provides minimum error, and supplies it to thesubtracter 405 and the adder 408.

[0079] In the MPEG 1 motion compensative prediction, there are threetypes of coding modes as shown in FIG. 3: an intra-frame coding mode(I-Picture); a forward motion compensative inter-frame predictive codingmode (P-Picture); and a bidirectional motion compensative inter-framepredictive coding mode (B-Picture). With regard to I pictures(intra-frame coding mode frame images) F(0) and F(9), the motioncompensative prediction is not carried out, that is, the predicted frameimage 210 is not generated. Since I pictures are used as a referenceimage for the motion compensative prediction, a high quality decodedimage is required of the I pictures. The amount of codes, on the otherhand, considerably increases because the motion compensative predictionis not performed. With regard to P pictures (forward motion compensativeinter-frame predictive coding mode frame images) F(3) and F(6), themotion compensative prediction is carried out using only a precedingimage, such as F(0) for F(3), F(3) for F(6). Since the P pictures areoccasionally used as the reference image of the motion compensativeprediction, their quality must be kept at a certain degree. With regardto B pictures (bidirectional motion compensative inter-frame predictivecoding mode frame images) F(1) and F(2), F(4) and F(5), and F(7) andF(8), the motion compensative prediction is performed using two images,preceding and following ones. Since the B pictures are not used as thereference image of the motion compensative prediction, roughquantization is possible. The bidirectional motion compensativeprediction can reduce the code amount because the decoded images can beobtained only from the motion vectors if the preceding and following Ipictures and P pictures have high quality in a stream of motionsequences.

[0080] When the current coded data frame memory 404 takes the codingmode as shown in FIG. 3, it outputs the frame images in the order ofF(0)-F(3)-F(1)-F(2)-F(6)-F(4)-F(5)-F(9)-F(7)-F(8).

[0081] The image coded data re-encoding apparatus 30 generates thesecond image coded data 240 from the first image coded data 220 thecoding processor 40 has generated by applying the coding on the inputimage signal 200 by transforming at least one of the “volume of thecoded data”, “size of the coded image”, “coding systems” and “sequenceof the images”. Specifically, the image coded data analyzer 310 receivesthe first image coded data 220 from the coding processor 40, andanalyzes the data to generate the coded data after signal processing 221after the coding. In addition, it extracts the multiple signals 222associated with the first image coded data in the process of generatingthe coded data after signal processing 221, thereby outputting themultiple signals. Subsequently, the image coded data synthesizer 320generates the second image coded data 240 from the coded data aftersignal processing 221 and the multiple signals 222 associated with thefirst image coded data, and outputs it to the decoding processor 50.Thus, the image coded data synthesizer 320 is paired with the imagecoded data analyzer 310. Considering the image coded data analyzer 310as an integral part of an image decoder, which carries out the decodingof the first image coded data 220 halfway, the image coded datasynthesizer 320 can be considered as an integral part of an image coder,which performs the re-encoding of the coded data after signal processing221 which has been decoded halfway by the image coded data analyzer 310.

[0082] This will be described in more detail with reference to thedrawings.

[0083] The image coded data analyzer 310 of the image coded datare-encoding apparatus 30 receives the first image coded data 220 whichis obtained by coding in the coding processor 40 the digital input imagesignal 200 like a digital motion image signal. The image coded dataanalyzer 310 has a function to perform the variable length decoding ofthe first image coded data 220, and a function to carry out the inversequantization of the decoded quantization indices, and analyzes the firstimage coded data 220 when it is input. Specifically, it carries out afirst digital signal processing on the input first image coded data 220by using the variable length decoding and inverse quantizationfunctions, thereby supplying the image coded data synthesizer 320 withresults of the first digital signal processing, that is, the coded dataafter signal processing 221 and the multiple signals 222 associated withthe first image coded data, which has been extracted from the firstimage coded data 220 during the first digital signal processing.

[0084] On the other hand, the image coded data synthesizer 320 has afunction to perform on the coded data after signal processing 221 fedfrom the image coded data analyzer 310 a coefficient correction thatdeletes, adds, or corrects the transform coefficients of the coded dataafter signal processing 221. The image coded data synthesizer 320 hasanother function to quantize the data which has undergone thecoefficient correction, and still another function to perform thevariable length coding of the quantization indices. The image coded datasynthesizer 320, receiving the coded data after signal processing 221,the multiple signals 222 associated with the first image coded data, andthe information 223 instructing the transform, carries out the synthesisof the coded data by using the functions such as the coefficientcorrection, quantization and variable length coding. Specifically, itperforms a second digital signal processing of the coded data aftersignal processing 221 based on the multiple signals 222 associated withthe first image coded data and the information 223 instructing thetransform, thereby generating the second image coded data 240 as aresult of the second digital signal processing. In this process, themultiple signals 222 associated with the first image coded data, whichis extracted from the first image coded data 220 during the firstdigital signal processing by the image coded data analyzer 310, is usedwhen the first image coded data 220 is transformed, without beingdecoded to an image, to the second image coded data 240. The secondimage coded data 240 thus generated is transmitted through acommunication channel, or recorded on a storage medium such as a CD-ROM,or a video tape, to be supplied to the decoding processor 50.

[0085] The second image coded data 240 as transmitted/recordedinformation, which has been transmitted through the communicationchannel or recorded on the storage medium such as CD-ROM or video tape,is decoded by the decoding processor 50 to be output as the decodedimage signal 250. In other words, the decoding processor 50 provides aninverse process of the coding processor 40.

[0086]FIG. 4 is a block diagram illustrating a concrete configuration ofthe decoding processor 50 to explain its operation. In this figure, thevariable length decoder 501, inverse quantizer 502 and inversetransformer 503 function as an inverse transformer which implements thebasic function for decoding the second image coded data 240 into thedecoded image signal 250. The remaining portion is added to implementmotion compensative prediction. In FIG. 4, the reference numerals 241,242 and 243 designate quantization indices, quantization parameters, anddecoded motion vectors, respectively, all of which are obtained by thevariable length decoding of the second image coded data 240 by thevariable length decoder 501. The reference numeral 244 designatestransform coefficients generated by the inverse quantization of thequantization indices 241 by the inverse quantizer 502, and 245designates a prediction error frame image generated by the inverse DCTof the transform coefficients 244 by the inverse transformer 503. Thereference numeral 504 designates an adder for adding the predictionerror frame image 245 to a predicted frame image 248 fed from the motioncompensative predictor described later, and 246 designates a currentframe image output from the adder 504. The reference numeral 505designates a current decoded data frame memory, into which the currentframe image 246 is stored, and from which the current frame image 246 isread as a decoded image signal 250. The reference numeral 506 designatesa preceding decoded data frame memory, into which the current frameimage 246 is stored, and from which it is read in the next cycle as apreceding frame image 247. The reference numeral 507 designates a motioncompensative predictor for generating a predicted frame image 248, whichis supplied to the adder 504, from the preceding frame image 247 and thecurrent frame image 246 on the basis of the decoded motion vectors 243from the variable length decoder 501.

[0087] The variable length decoder 501 of the decoding processor 50 withthe arrangement as shown in FIG. 4 receives the second image coded data240 which has been generated by applying the first and second digitalsignal processings to the first image coded data 220 in the image codeddata re-encoding apparatus 30, and recorded on the storage medium suchas the CD-ROM or the video tape. The variable length decoder 501performs the variable length decoding of the input second image codeddata 240 to decode it to the quantization indices 241 and to generatethe quantization parameters 242 and decoded motion vectors 243.Subsequently, the inverse quantizer 502 performs the inverse scalarquantization of the quantization indices 241 decoded by the variablelength decoder 501 in accordance with the quantization parameters 242from the variable length decoder 501, thereby obtaining the inversequantized transform coefficients 244. Then, the inverse transformer 503carries out the inverse DCT of the transform coefficients 244 which hasundergone the inverse quantization in the inverse quantizer 502, thus togenerate the prediction error frame image 245. The adder 504 adds theprediction error frame image 245 which has undergone the inversetransform in the inverse transformer 503 to the predicted frame image248 fed from the motion compensative predictor 507 to generate thecurrent frame image 246 to be decoded. The current frame image 246 isstored in the current decoded data frame memory 505, and is readtherefrom as the decoded image signal 250. The current frame image 246is also stored in the preceding decoded data frame memory 506 so that itis read during the motion compensative prediction in the next cycle asthe preceding frame image 247 which has already been decoded, and issupplied to the motion compensative predictor 507. The motioncompensative predictor 507 generates in accordance with the decodedmotion vectors 243 fed from the variable length decoder 501 thepredicted frame image 248 to be supplied to the adder 504 from thepreceding frame image 247 which has already been decoded and the currentframe image 246 which is output from the adder 504.

[0088] Although in the above description, the motion compensativeprediction is carried out in the coding processor 40 and the decodingprocessor 50, the motion compensative prediction may be omitted.

[0089] According to the first embodiment, the multiple signals 222associated with the first image coded data is employed in the seconddigital signal processing for generating the second image coded data240, which multiple signals 222 are extracted in the process of applyingthe first digital signal processing to the first image coded data 220.This makes it unnecessary to add special information for the seconddigital signal processing, and hence reduces the information amount,resulting in information efficient apparatus.

[0090] Embodiment 2

[0091] Although the foregoing embodiment 1 used the multiple signals 222associated with the first image coded data, which are extracted in theprocess of applying the first digital signal processing to the firstimage coded data 220, to generate the second coded data 240 by applyingthe second digital signal processing to the coded data after signalprocessing 221, the multiple signals associated with the first imagecoded data can be obtained by other ways. For example, information whichis used for generating the first image coded data 220 by coding theinput image signal 200 in the coding processor 40, and which cannot beextracted in the process of applying the first digital signal processingto the first image coded data 220 in the image coded data re-encodingapparatus 30, can be combined with the first image coded data 220 to befed to the image coded data re-encoding apparatus 30 so that the imagecoded data re-encoding apparatus 30 separates the information from thefirst image coded data 220 as the multiple signals associated with thefirst image coded data which are used for performing the second digitalsignal processing on the first image coded data 220.

[0092]FIG. 5 is a block diagram showing an embodiment 2 of the imagecoded data re-encoding apparatus 30 in accordance with the presentinvention together with the coding processor 40 and the decodingprocessor 50, wherein the corresponding portions are designated by thesame reference numerals as in FIG. 1, and the description thereof isomitted here. In FIG. 5, the reference numeral 414 designates a combinerprovided in the coding processor 40 for combining, with the first imagecoded data 220 which is output from the variable length coder 403, theabove-mentioned information which is used by the transformer 401 and thequantizer 402 for generating the first image coded data 220 by codingthe input image signal 200 in the coding processor 40, and which cannotbe extracted in the process of applying the first digital signalprocessing to the first image coded data 220 in the image coded datare-encoding apparatus 30, and 260 designates combination data outputfrom the combiner 414. The reference numeral 340 designates a separatorprovided in the image coded data re-encoding apparatus 30 for separatingfrom the combination data 260 delivered from the coding processor 40 thefirst image coded data 220 and the information that cannot be extractedin the first digital data processing, and 224 designates multiplesignals associated with the first image coded data corresponding to theinformation which cannot be extracted in the first digital signalprocessing. The first image coded data 220 and the multiple signals 224associated with the first image coded data, which are separated by theseparator 340, are supplied to the image coded data analyzer 310 and theimage coded data synthesizer 320, respectively.

[0093] Next, the operation of the embodiment 2 will be described.

[0094] The coding processor 40 basically operates in the same manner asthat of the embodiment 1: It performs the coding of the digital inputimage signal 200 to obtain the first image coded data 220. Only, itdiffers from the embodiment 1 in the following: The information which isused for the coding by the transformer 401 and the quantizer 402, andwhich cannot be extracted in the process of performing the first digitalsignal processing on the first image coded data 220 by the image codeddata re-encoding apparatus 30, is sent to the combiner 414. The combiner414 combines the information with the first image coded data 220 outputfrom the variable length coder 403 to generate the combination data 260,and supplies it to the image coded data re-encoding apparatus 30. Here,the information which is output from the transformer 401 and thequantizer 402, and which cannot be extracted in the process of applyingthe first digital signal processing to the first image coded data 220,differs depending on the coding method employed. For example, when MPEG1 is employed, the parameter used for specifying the type of thetransformer 401 is output from the transformer 401, and the parametersused for specifying the characteristic of the quantizer 402 are outputfrom the quantizer 402.

[0095] In the image coded data re-encoding apparatus 30, receiving thecombination data 260 from the coding processor 40, the separator 340separates it to the first image coded data 220 and the multiple signals224 concerning the first image coded data associated with theinformation which cannot be extracted in the process of the firstdigital signal processing. The divided first image coded data 220 issupplied from the separator 340 to the image coded data analyzer 310.The image coded data analyzer 310 carries out the first digital signalprocessing of the first image coded data 220, and supplies the imagecoded data synthesizer 320 with the result of the first digital signalprocessing as the coded data after signal processing 221.

[0096] Accordingly, in this case also, the image coded data analyzer 310can be considered as a part of the image decoder. On the other hand, themultiple signals 224 concerning the first image coded data, which areseparated by the separator 340, are input to the image coded datasynthesizer 320. The image coded data synthesizer 320 paired with theimage coded data analyzer 310, receiving the coded data after signalprocessing 221 and the multiple signals 224 concerning the first imagecoded data, carries out the second digital signal processing inaccordance with the information 223 that commands the transform anddefines the data amount and image size to be transformed. Accordingly,in this case also, the image coded data synthesizer 320 can beconsidered as a part of the image coder. The image synthesis processingof the coded data in the image coded data synthesizer 320 is performedin a manner similar to that of the embodiment 1 except that the multiplesignals 224 concerning the first image coded data, which are separatedfrom the combination data 260 by the separator 340, are used instead ofthe multiple signals 222 associated with the first image coded data,which are extracted by the image coded data analyzer 310. The multiplesignals 224 concerning the first image coded data, which are used fortransforming the first image coded data 220 into the second image codeddata 240 without once decoding the first image coded data 220 into animage, also serves as the information for achieving improved images ascompared with the case where the multiple signals 222 associated withthe first image coded data is used. The second image coded data 240generated as the result of the second digital signal processing istransmitted through a communication channel or recorded on the storagemedium such as a CD-ROM or video tape, and is input to the decodingprocessor 50 which decodes it to the decoded image signal 250 in exactlythe same way as the decoding processor 50 of the embodiment 1.

[0097] Thus, the embodiment 2 uses, for the second digital signalprocessing in the image coded data synthesizer 320, the multiple signals224 which cannot be extracted in the process of the first digital signalprocessing. As a result, it has an advantage of achieving more efficienttransform than an apparatus which does not use the multiple signals 224.

[0098] Embodiment 3

[0099] The foregoing embodiments generate the second image coded data240 by applying the second digital signal processing to the coded dataafter signal processing 221 by using the multiple signals 222 or 224. Itmay also be possible to use, for carrying out the second digital signalprocessing of the first image coded data 220, multiple signalsassociated with the first image coded data 220, which are extracted orestimated from the coded data after signal processing 221 as informationneeded for re-encoding the coded data after signal processing 221. Inthis case, the coded data after signal processing 221 is obtained bydecoding the first image coded data 220 through the first digital signalprocessing using the image coded data analyzer 310 as an image decoderand the image coded data synthesizer 320 as an image coder.

[0100]FIG. 6 is a block diagram showing a third embodiment of the imagecoded data re-encoding apparatus 30 in accordance with the presentinvention, together with the coding processor 40 and decoding processor50, in which the corresponding portions to those of the embodiment 1 aredesignated by the same reference numerals, and the description thereofis omitted here. In this figure, the reference numeral 350 designates aninformation extractor/estimator, and 225 designates multiple signalsassociated with the first image coded data output from the informationextractor/estimator 350. The information extractor/estimator 350extracts or estimates from the coded data after signal processing 221the information which is needed for re-encoding the coded data aftersignal processing 221 in the second digital signal processing, andsupplies the resultant information to the image coded data synthesizer320 as the multiple signals 225 associated with the first image codeddata. In this case, the coded data after signal processing 221 isobtained by decoding the first image coded data 220 by applying thefirst digital signal processing to the image coded data 220 in the imagecoded data analyzer 310.

[0101] Next, the operation will be described.

[0102] The description is omitted here of the process of generating thefirst image coded data 220 by coding the input image signal 200 with thecoding processor 40, and the process of generating the decoded imagesignal 250 by decoding the second image coded data 240 with the decodingprocessor 50, because they are the same as those of the embodiment 1.Thus, the operation of only the image coded data re-encoding apparatus30 will be described here.

[0103] In the image coded data re-encoding apparatus 30, receiving thefirst image coded data 220 from the coding processor 40, the image codeddata analyzer 310 performs the first digital signal processing of thefirst image coded data 220 to decode it. The decoded image data is fedto the information extractor/estimator 350 and the image coded datasynthesizer 320 as the coded data after signal processing 221. Theinformation extractor/estimator 350 extracts or estimates from the codeddata after signal processing 221 fed from the image coded data analyzer310 the multiple signals 225 associated with the first image coded data,which are needed for the second digital signal processing in the imagecoded data synthesizer 320, and supplies them to the image coded datasynthesizer 320. The image coded data synthesizer 320 is provided withthe information 223 which defines the data amount and image size to betransformed and commands the transform, in addition to the multiplesignals 225 associated with the first image coded data, and the codeddata after signal processing 221 from the image coded data analyzer 310.The image coded data synthesizer 320 applies the second digital signalprocessing to the coded data after signal processing 221 to generate thesecond image coded data 240. In this case, the multiple signals 225associated with the first image coded data which are extracted orestimated from the coded data after signal processing 221 by theinformation extractor/estimator 350 are not only used for decoding thefirst image coded data 220 into an image, but also used for generatingthe second image coded data 240. The thus generated second image codeddata 240 is fed from the image coded data re-encoding apparatus 30 tothe decoding processor 50.

[0104] The embodiment 3 with such an arrangement has an advantage thatthe configuration of the image coded data re-encoding apparatus 30 issimplified. This is because no special processing is required fordecoding since the multiple signals 225 associated with the first imagecoded data 220, which are needed for the second digital signalprocessing by the image coded data synthesizer 320, are extracted orestimated from the coded data after signal processing 221 which are oncedecoded from the first image coded data 220.

[0105] Embodiment 4

[0106]FIG. 7 is a block diagram showing the internal configuration ofthe image coded data analyzer 310 and the image coded data synthesizer320 as an embodiment 4 of the image coded data re-encoding apparatus 30in accordance with the present invention, which can reduce the amount ofdata between the first image coded data 220 and the second image codeddata 240. In this figure, the reference numeral 311 designates avariable length decoder for carrying out variable length decoding of thefirst image coded data 220 delivered from the coding processor 40, and226 designates quantization indices, the result of the decoding producedfrom the variable length decoder 311. The reference numeral 312designates an inverse quantizer for performing inverse quantization ofthe quantization indices 226, and 227 designates transform coefficients,the result of the inverse quantization by the inverse quantizer 312. Theinversely quantized transform coefficients 227 is output as the codeddata after signal processing 221. The image coded data analyzer 310 inaccordance with the present embodiment 4 includes these variable lengthdecoder 311 and inverse quantizer 312.

[0107] The reference numeral 321 designates a coefficientdeletion/addition/correction portion for deleting, adding or correctinga part of the inversely quantized transform coefficients 227 deliveredfrom the image coded data analyzer 310 as the coded data after signalprocessing 221 in response to the information 223 that commands thetransform and defines the data amount to be transformed. The referencenumeral 228 designated corrected transform coefficients, the result ofthe coefficient correction by the coefficientdeletion/addition/correction portion 321, and 229 designatesquantization indices, the result of the quantization, produced from aquantizer 322. The reference numeral 323 designates a variable lengthcoder which codes the quantization indices 229, and supplies thedecoding processor 50 with the resultant second image coded data 240.The image coded data synthesizer 320 in accordance with the embodiment 4includes the coefficient deletion/addition/correction portion 321,quantizer 322 and variable length coder 323.

[0108] Next, the operation will be described.

[0109] It is assumed here, that the coding processor 40 and the decodingprocessor 50 employ a coding system based on the transform codingincluding the coding and quantization as a basic function, and that theimage coded data analyzer 310 performs a part of the decoding, whereinthe coding processor 40 generates the first image coded data 220 bycoding the input image signal 200, and supplies it to the image codeddata re-encoding apparatus 30, and the decoding processor 50 generatesthe decoded image signal 250 by decoding the second image coded data 240the image coded data re-encoding apparatus 30 outputs. In this case, theimage coded data analyzer 310 extracts the transform coefficients or thequantization indices by carrying out the inverse quantization of thefirst image coded data 220, and the image coded data synthesizer 320deletes a part of the inverse quantized transform coefficients or thequantization indices, and corrects the remaining transform coefficientsand the quantization indices in accordance with the ratio of the amountof the data to be transformed. This can facilitate the transformconsidering the image quality after the inverse transform as comparedwith the case where part of the transform coefficients or thequantization indices is simply deleted.

[0110] Referring the drawings, the operation will be described in moredetail.

[0111] The variable length decoder 311, receiving the first image codeddata 220, carries out the variable length decoding referring a tableprepared in advance to produce the combination data 260 corresponding tthe first image coded data 220. An example of the table is shown inTable 1. TABLE 1 occurrence probability data code (coded data) 0.3 1 000.25 2 01 0.2 3 11 0.1 4 101 0.08 5 1000 0.07 6 1001

[0112] In this table, each of six data is assigned a code correspondingto the possibility of occurrence such that a shorter code is assigned todata with higher possibility of occurrence, and vice versa. Thus,assignment of codes with different length is performed in accordancewith the possibility of occurrence of the quantization indices. Thevariable length decoder 311 carries out the variable length decoding byextracting data corresponding to the code (coded data) from the table.

[0113] Thus, the quantization indices 226 output from the variablelength decoder 311 are input to the inverse quantizer 312. The inversequantizer 312 generates the inversely quantized transform coefficients227 by performing the inverse quantization of the quantization indices226 in accordance with the quantization parameters (not shown), andsupplies it to the image coded data synthesizer 320 as the coded dataafter signal processing 221. Incidentally, the quantization in thedigital processing can usually be achieved by division, whereas theinverse quantization is achieved by multiplication.

[0114] The coefficient deletion/addition/correction portion 321 of theimage coded data synthesizer 320, receiving the information 223 whichcommands the transform, deletes a part of the coded data after signalprocessing 221 fed from the image coded data analyzer 310 in accordancewith the data amount to be transformed instructed by the information 223commanding transform, and carries out the coefficient correction of theremainder of the coded data in accordance with the ratio of the dataamount to be transformed which is defined by the information 223commanding transform.

[0115] In this embodiment 4 of the image coded data re-encodingapparatus 30, the data amount is reduced through the transform. Whenreducing the data amount of the transform coefficients, it isadvantageous to start deletion of the transform coefficients from higherfrequency components because lower frequency components are moresignificant than the higher frequency components of the transformcoefficients. In this case, although simple deletion of the data in aparticular region of the transform coefficients is effective forreducing the data amount itself, this will effect on the quality ofimages decoded from the transform coefficients with the reduced dataamount. To prevent this, the present embodiment 4 not only deletes partof the transform coefficients 227, but also corrects the remainder ofthe transform coefficients 227 in accordance with the ratio of the dataamount to be transformed which is instructed by the information 223commanding transform. In this process, the effect on the decoded imagethe deleted part will produce is predicted, so that the correction ofthe remainder of the transform coefficients 227 is achieved such thatthe effect becomes minimum.

[0116] The coefficient deletion/addition/correction portion 321 deletesthe part of the transform coefficients 227 in this way, and thecorrected transform coefficients 228 generated by correcting theremainder are input to the quantizer 322. The quantizer 322 carries outthe quantization of the corrected transform coefficients 228 to generatethe quantization indices 229, and supplies them to the variable lengthcoder 323. The variable length coder 323 performs the variable lengthcoding of the quantization indices 229 in accordance with thequantization parameters output from the quantizer 322 to generate thesecond image coded data 240, and delivers it to the decoding processor50.

[0117] According to the embodiment 4, the deletion of the part of thetransform coefficients 227, which are transferred from the image codeddata analyzer 310 as the coded data after signal processing 221, enablesthe data amount to be reduced. In addition, the correction of theremainder of the transform coefficients 227 in accordance with the ratioof its data amount enables the decoded image quality to be improved ascompared with that obtained by simply thinning out the transformcoefficients.

[0118] Embodiment 5

[0119] In the embodiment 4, the data amount is reduced between the firstimage coded data 220 and the second image coded data 240 by deleting apart of the reversely quantized transform coefficients or thequantization indices, and by correcting the transform coefficients inaccordance with the amount of data to be transformed. A part of thetransform coefficients or the quantization indices, however, may bedeleted by weighting the transform coefficients or the quantizationindices to be reduced with the neighboring transform coefficients or thequantization indices, which is implemented in the embodiment 5.

[0120] In the embodiment 5 of the image coded data re-encodingapparatus, the image coded data analyzer 310 as shown in FIG. 7 carriesout the processings as follows: First, the variable length decoder 311decodes the first image coded data 220 into the quantization indices226. Then, the inverse quantizer 312 performs the inverse quantizationof the decoded quantization indices 226, and transfers the resultanttransform coefficients 227 to the image coded data synthesizer 320 asthe coded data after signal processing 221. The image coded datasynthesizer 320 receives the transform coefficients 227 with thecoefficient deletion/addition/correction portion 321 which deletes partof the transform coefficients 227 after weighting the transformcoefficients 227 with its neighboring transform coefficients.Specifically, the coefficient deletion/addition/correction portion 321examines, before deleting part of the transform coefficients 227, therelationship between the transform coefficients to be deleted and theirneighboring transform coefficients, performs weighting such that thedeletion has a minimum effect on the quality of the decoded image, anddeletes the transform coefficients to be deleted.

[0121] The embodiment 5 also, as the embodiment 4, enables the decodedimage quality to be improved as compared with that obtained by simplythinning out the transform coefficients.

[0122] Embodiment 6

[0123] Although the data amount is reduced between the first image codeddata 220 and the second image coded data 240 in the embodiments 4 and 5,it can be increases by adding new transform coefficients or quantizationindices. In this case, the transform coefficients, which are added tothe inversely quantized transform coefficients or quantization indices,are corrected in accordance to the ratio of the amount of data to betransformed, which is implemented in the embodiment 6.

[0124] In the embodiment 6 of the image coded data re-encodingapparatus, the image coded data analyzer 310 as shown in FIG. 7 carriesout the processings as follows: First, the variable length decoder 311decodes the first image coded data 220 into the quantization indices226. Then, the inverse quantizer 312 performs the inverse quantizationof the decoded quantization indices 226, and transfers the resultanttransform coefficients 227 to the image coded data synthesizer 320. Theimage coded data synthesizer 320 receives the transform coefficients 227with the coefficient deletion/addition/correction portion 321 whichcarries out the addition of new transform coefficients to increase theamount of data of the second image coded data 240 by using the transformcoefficients 227 and a picture type which is obtained in the decodingprocedure of the image coded data. Specifically, the coefficientdeletion/addition/correction portion 321 carries out the correction ofthe newly added transform coefficients such that the effect of additionon the quality of the decoded image becomes minimum, in accordance withthe ratio of the data amount defined by the information that commandsthe transform.

[0125] Considering the effect on the quality of the decoded image ofincreasing the data amount between the first image coded data 220 andthe second image coded data 240, it will be advantageous to add the highfrequency components of the transform coefficients or the quantizationindices as in the case of reducing the data amount. Furthermore, theaddition of the transform coefficients or the quantization indices inthe higher frequency domain induces a greater change in the data amountthan that in the lower frequency domain.

[0126] Thus, the embodiment 6 corrects the newly added transformcoefficients or the quantization indices in accordance with the ratio ofthe amount of data to be transformed. This makes it possible to add thedata considering the image quality after the inverse transform, therebyachieving a higher image quality than that obtained by simply thinningout the transform coefficients.

[0127] Embodiment 7

[0128] The embodiment 6 corrects the newly added transform coefficientsor the quantization indices in accordance with the ratio of the amountof data to be transformed, when adding the transform coefficients or thequantization indices to the inversely quantized transform coefficientsor the quantization indices to increase the amount of data between thefirst image coded data 220 and the second image coded data 240. Theaddition of the transform coefficients or quantization indices may beperformed after predicting the transform coefficients or quantizationindices including the newly added transform coefficients or quantizationindices and their neighboring transform coefficients or quantizationindices, which is implemented in the embodiment 7.

[0129] In the embodiment 7 of the image coded data re-encodingapparatus, the image coded data analyzer 310 as shown in FIG. 7 carriesout the processings as follows: First, the variable length decoder 311decodes the first image coded data 220 into the quantization indices226. Then, the inverse quantizer 312 performs the inverse quantizationof the obtained quantization indices 226, and transfers the resultanttransform coefficients 227 to the image coded data synthesizer 320. Theimage coded data synthesizer 320 receives the transform coefficients 227with the coefficient deletion/addition/correction portion 321 whichcarries out prediction of the transform coefficients including the newlyadded transform coefficients and their neighboring transformcoefficients, followed by the addition of the transform coefficients,when increasing the data amount of the second image coded data 240 afterthe transform by using the received transform coefficients 227.

[0130] Thus, the embodiment 7 adds the transform coefficients orquantization indices after predicting the transform coefficients orquantization indices to be added and their neighbors. This makes itpossible to implement more vivid images, providing an advantage ofachieving the transform resulting in higher image quality than thatobtained by the transform which simply thins out the transformcoefficients.

[0131] Embodiment 8

[0132]FIG. 8 is a block diagram showing the internal configuration ofthe image coded data analyzer 310 and the image coded data synthesizer320 of an eighth embodiment of the image coded data re-encodingapparatus 30 in accordance with the present invention, which reduces thedata amount between the first image coded data 220 and the second imagecoded data 240. In this figure, the reference numeral 230 designatescoded picture information as a coding parameter indicating the picturetype. The coded picture information 230 is output as the result of thedecoding from the variable length decoder 311 which performs thevariable length decoding of the first image coded data 220 supplied fromthe coding processor 40. The remaining portions are the same as those ofFIG. 7, and the description thereof is omitted here. The variable lengthdecoder 311, however, differs from that of the embodiment 4 in that itoutputs the coded picture information 230 besides the quantizationindices 226. In addition, the coefficient deletion/addition/correctionportion 321 differs from that of the embodiment 4 in that it deletes,adds or corrects part of the transform coefficients 227 by using thecoded picture information 230 besides the amount of data to betransformed which is instructed by the information 223 commanding thetransform. The coded picture information 230 here is a parametermultiplexed picture by picture to represent the attributes such as thesize of the picture, coding type of the picture (that is, theintra-frame coding, unidirectional motion compensative inter-framepredictive coding, or bidirectional motion compensative inter-framepredictive coding), maximum value of vectors used by the picture, andadaptive parameters used by the picture.

[0133] The operation will now be described.

[0134] The eighth embodiment of the image coded data re-encodingapparatus implements the transform that can reduce the total degradationof the image quality by increasing the ratio of deletion of thetransform coefficients or quantization indices included in the picturetypes which will not be used in the future prediction. This is performedby using the transform coefficients or quantization indices obtained bythe inverse quantization of the first image coded data 220 in the imagecoded data analyzer 310, and the coded picture parameter obtained in thecourse of decoding the first image coded data 220.

[0135] In the image coded data analyzer 310 as shown in FIG. 8, thevariable length decoder 311 provides the inverse quantizer 312 with thequantization indices 226 obtained as a result of decoding the firstimage coded data 220, and supplies the image coded data synthesizer 320with the coded picture information 230 obtained in the course of thedecoding. The inverse quantizer 312 carries out the inverse quantizationof the received quantization indices 226, and sends the resultanttransform coefficients 227 to the image coded data synthesizer 320 asthe coded data after signal processing 221. In the image coded datasynthesizer 320, on the other hand, the coefficientdeletion/addition/correction portion 321 receives the information 223,which commands the transform and defines the amount of data to betransformed, and deletes part of the received transform coefficients227. When the information 223 indicates the coded picture which will notbe used for the prediction in the future coding, the ratio of deletionof the transform coefficients is increased. The received coded pictureinformation 230 includes, as described above, the coding type of thepicture. When the coding type indicates the bidirectional motioncompensative inter-frame prediction coding according to the MPEG 1, forexample, the picture information is not used for the future coding.Thus, even if the reduction of the data amount results in thedegradation of the image quality, there is no fear that it willcontinue. As a result, an increase in the deletion ratio of thetransform coefficients in such picture information will improve theefficiency of the reduction of the data amount.

[0136] Thus, according to the embodiment 8, an advantage is obtainedthat the data reduction can be implemented with high total efficiency byfurther reducing the data amount when the coded frame is not used in thenext coding interval.

[0137] Embodiment 9

[0138] Although the embodiment 8 handles the case in which the reductionratio of the transform coefficients is increased when the information223 indicates that the coded picture will not be used in the futureprediction, the reduction ratio of the transform coefficients may bereduced when the information indicates that the coded picture will beused in the following prediction. More specifically, when the picturetype indicates the use in the future coding, the reduction ratio of thetransform coefficients or quantization indices will be reduced by usingthe transform coefficients or quantization indices obtained by theinverse quantization of the first image coded data 220 in the imagecoded data analyzer 310 as shown in FIG. 8, and by using the picturetype obtained in the course of decoding the first image coded data 220.Thus, the transform is implemented which can prevent the degradationfrom being continued to the future by the prediction.

[0139] As a result, the embodiment 9 has an advantage of achieving datareduction with higher total efficiency by decreasing the reduction inthe amount of data of the coded data, when the coded frame is used inthe next coding interval.

[0140] Embodiment 10

[0141]FIG. 9 is a block diagram showing the internal configuration ofthe image coded data analyzer 310 and image coded data synthesizer 320of an embodiment 10 of the image coded data re-encoding apparatus 30 inaccordance with the present invention, which reduces the amount of databetween the first image coded data 220 and the second image coded data240. In this figure, the reference numeral 231 designates coded blockinformation, one of the coding parameters indicating the predictive typeof the image block. The coded block information 231 is output as theresult of decoding by the variable length decoder 311 which carries outthe variable length decoding of the first image coded data 220 suppliedfrom the coding processor 40. The remaining portions are designated bythe same reference numerals as in FIG. 8, and the description thereof isomitted here. The variable length decoder 311, however, differs fromthat of the embodiment 8 in that it outputs the coded block information231 besides the quantization indices 226 and the coded pictureinformation 230. In addition, the coefficientdeletion/addition/correction portion 321 differs from that of theembodiment 8 in that it deletes, adds or corrects part of the transformcoefficients 227 by using the coded block information 231 besides thecoded picture information 230 and the amount of data to be transformed,which is instructed by the information 223 commanding the transform. Thecoded block information 231 is the information about the coded block(often called micro-block in the MPEG 1) which is the minimum unit ofcoding and represents quantization parameters, motion vectors, and thepresence or absence of the motion compensative prediction, which areused in the coded block.

[0142] Next, the operation will be described.

[0143] The tenth embodiment of the image coded data re-encodingapparatus implements the transform that can reduce the total degradationof the image quality by increasing the ratio of deletion of thetransform coefficients or quantization indices included in the imageblocks which are not used in the prediction, even if they belong to thepicture types which will be used in the future coding. This is performedby using the transform coefficients or quantization indices obtained bythe inverse quantization of the first image coded data 220 in the imagecoded data analyzer 310, and the picture types obtained in the course ofdecoding the first image coded data 220.

[0144] In the image coded data analyzer 310 as shown in FIG. 9, thevariable length decoder 311 provides the inverse quantizer 312 with thequantization indices 226 obtained as a result of decoding the firstimage coded data 220, and supplies the image coded data synthesizer 320with the coded picture information 230 and coded block information 231which are obtained in the course of the decoding. The inverse quantizer312 carries out the inverse quantization of the received quantizationindices 226, and sends the resultant transform coefficients 227 to theimage coded data synthesizer 320 as the coded data after signalprocessing 221. In the image coded data synthesizer 320, on the otherhand, the coefficient deletion/addition/correction portion 321 receivesthe transform coefficients 227, coded picture information 230 and codedblock information 231 besides the information 223, which commands thetransform and defines the amount of data to be transformed, and deletespart of the received transform coefficients 227. In the course of this,the coefficient deletion/addition/correction portion 321 decides on thebasis of the received coded block information 231 whether theinformation of the image block is used in the future coding, not on thecoded picture basis but on the image block basis which enables finercontrol. If the result of this indicates that the image block is notused in prediction in the future coding, even though the coded picturewill be used in the prediction in the future coding, the deletion ratioof the transform coefficients is increased.

[0145] Thus, according to the embodiment 10, an advantage is obtainedthat the control based on a finer unit becomes possible and higherquality transform is achieved, because the decision is made whether thedeletion ratio of the transform coefficients or quantization indicesshould be increased or not by using the coded block information 231 inaddition to the coded picture information 230.

[0146] Embodiment 11

[0147]FIG. 10 is a block diagram showing the internal configuration ofthe image coded data analyzer 310 and image coded data synthesizer 320of an embodiment 11 of the image coded data re-encoding apparatus 30 inaccordance with the present invention, in which the decoding procedureof the first image coded data 220 differs from that of the second imagecoded data 240. In this figure, the reference numeral 311 designates avariable length decoder which carries out the variable length decodingof the first image coded data 220 supplied from the coding processor 40.The reference numeral 226 designates quantization indices, 230designates coded picture information, 231 designates coded blockinformation, 232 designates quantization parameter information, and 233designates motion vector information, all of which are output from thevariable length decoder 311 as coding parameters as the result of thedecoding, and are supplied to the image coded data synthesizer 320 asthe coded data after signal processing 221. The variable length decoder311 with such an arrangement is included in the image coded dataanalyzer 310 in this embodiment 11. The quantization parameterinformation 232 and motion vector information 233 are handled as one ofthe coded block information 231.

[0148] The reference numeral 324 designates a coding parametercorrection/transform portion which transforms the coding parameters suchas the quantization indices 226, coded picture information 230, codedblock information 231, quantization parameter information 232 and motionvector information 233 fed from the image coded data analyzer 310 as thecoded data after signal processing 221 so that they match the codingsystem after the transform. The reference numeral 323 designates avariable length coder that carries out coding of the transformed outputfrom the coding parameter correction/transform portion 324, and suppliesthe resultant second image coded data 240 to the decoding processor 50.The coding parameter correction/transform portion 324 and variablelength coder 323 are included in the image coded data synthesizer 320 ofthe embodiment 11.

[0149] Next, the operation will be described.

[0150] The following processing is carried out to make differencebetween the decoding procedure of the first image coded data 220 inputto the image coded data analyzer 310 and that of the second image codeddata 240 output from the image coded data synthesizer 320. For example,let us consider the case where the input first image coded data 220 isbased on the MPEG 1, and the output second image coded data 240 is basedon H.261 defining the coding system for visual telephone and videoconference. In the image coded data analyzer 310, the variable lengthdecoder 311 extracts from the input first image coded data 220 based onthe MPEG 1 the coding parameters such as quantization indices 226, codedpicture information 230, coded block information 231, quantizationparameter information 232 and motion vector information 233, andsupplies them to the image coded data synthesizer 320 as the coded dataafter signal processing 221. In the image coded data synthesizer 320,the coding parameter correction/transform portion 324 receives the codeddata after signal processing 221, and transforms the coding parametersin the MPEG 1 representation into those in the H.261 representation.

[0151] More concrete description will be provided of the transform fromthe MPEG 1 image coded data to the H.261 image coded data, taking themotion vector information 233 as an example. Although {fraction (1/2)}pixel motion vectors are available in the MPEG 1, only integer multipleaccuracy motion vectors are available in the H.261. Accordingly, thecoding parameter correction/transform portion 324 carries out thetransform in which it extracts only the integer portion of each of theMPEG 1 motion vectors which is considered optimum, and uses it as theH.261 motion vectors. Likewise, the coding parameters such as thequantization parameter information 232 and quantization indices 226 aretransformed into parameter values which considered optimum in the H.261unless they are used in exactly the same sense in both the MPEG 1 andH.261. The coding parameters transformed by the coding parametercorrection/transform portion 324 such that they match the H.261 codingsystem are synthesized to the second image coded data 240 by thevariable length coder 323 and is output therefrom.

[0152] Thus, according to the embodiment 11, it is not necessary todecode the first image coded data 220 to an image once, and thenre-encodes the image by an image coder based on the required codingsystem, thereby offering an advantage of implementing a small, low costapparatus. This holds true even when the first image coded data 220input to the image coded data analyzer 310 is transformed and outputfrom the image coded data synthesizer 320 as the second image coded data240 which is processed in the decoding procedure different from that ofthe first image coded data 220.

[0153] Embodiment 12

[0154]FIG. 11 is a block diagram showing the internal configuration ofthe image coded data analyzer 310 and image coded data synthesizer 320of an embodiment 12 of the image coded data re-encoding apparatus 30 inaccordance with the present invention, which transforms image sizebetween the first image coded data 220 and the second image coded data240. In this figure, the same or like portions are designated by thesame reference numerals as in FIG. 7, and the description thereof isomitted here. The present embodiment 12 differs from the embodiment 4 inthat the image size is defined by the information 223 which commands thetransform, and that the coefficient deletion/addition/correction portion321 deletes or corrects the transform coefficients 227 which areobtained through the inverse quantization by the inverse quantizer 312,by using the image size instructed by the information 223 commanding thetransform.

[0155] Next, the operation will be described.

[0156] Let us assume that the transform is carried out between the firstimage coded data 220 which is input to the image coded data analyzer 310and the second image coded data 240 which is output from the image codeddata synthesizer 320, each including an image signal of a differentimage size, and that the coding processor 40 which generates the firstimage coded data 220 and the decoding processor 50 which decodes thesecond image coded data 240 carry out processing based on transformcoding including the motion compensative prediction, transform andquantization as shown in FIGS. 2 and 4, respectively. When the inverselyquantized transform coefficients or quantization indices, which areextracted in the image coded data analyzer 310, are increased ordecreased, they are corrected in accordance with the ratio of the imagesizes to be transformed. This makes it possible to reduce thesubstantial degradation in the resolution or unnatural images whichreadily occur during the transform.

[0157] Referring to FIG. 11, the present embodiment will be described inmore detail.

[0158] In the image coded data analyzer 310 as shown in FIG. 11, thevariable length decoder 311 decodes the first image coded data 220 tothe quantization indices 226. The inverse quantizer 312 carries outinverse quantization, and supplies the resultant transform coefficients227 to the image coded data synthesizer 320 as the coded data aftersignal processing 221. In the image coded data synthesizer 320, thecoefficient deletion/addition/correction portion 321 receives thetransform coefficients 227 together with the information 223 commandingthe transform. The coefficient deletion/addition/correction portion 321performs revision like deletion/addition/correction of the transformcoefficients to be increased or decreased in accordance with the imagesizes to be transformed which are defined by the information 223commanding the transform. When reducing the image size, for example, thenumber of samplings of the image after transform is reduced as comparedwith that of the original image, and hence the frequency components ofthe image after transform will be lowered. Accordingly, some form ofband limit is required, which is performed on the transform coefficients227. Thus, the revision is carried out in transforming the coded data ofthe original image to that of a smaller size image by suppressing highfrequency components. The revised corrected transform coefficients 228is fed from the coefficient deletion/addition/correction portion 321 tothe quantizer 322 which generates the quantization indices 229 by thequantization. Then, the variable length coder 323 applies the variablelength coding to the quantization indices 229, and supplies theresultant second image coded data 240 to the decoding processor 50.

[0159] Thus, according to the embodiment 12, since the transformcoefficients to be increased or decreased are corrected in accordancewith the image sizes to be transformed when performing the transform ofthe coded data involving the image size transform, an advantage isgained that it becomes possible to prevent the substantial degradationin the resolution or the occurrence of unnatural images, and thedegradation in the image quality after the image size transform.

[0160] Embodiment 13

[0161] Although the transform coefficients to be increased or decreasedare revised in accordance with the ratio of the image sizes which aretransformed between the first image coded data 220 and the second imagecoded data 240 in the embodiment 12, the dimension of the motion vectorsused for the motion compensation may be revised in accordance with theratio of the image sizes to be transformed, to transform the first imagecoded data 220 to the second image coded data 240 of a different imagesize. This is implemented by an embodiment 13.

[0162]FIG. 12 is a block diagram showing the internal configuration ofthe image coded data analyzer 310 and image coded data synthesizer 320of the embodiment 13 of the image coded data re-encoding apparatus 30 inaccordance with the present invention. In this figure, the referencenumeral 233 designates motion vector information for motion compensationwhich is output from the variable length decoder 311 in the course ofvariable length decoding of the first image coded data 220 supplied fromthe coding processor 40. The remaining portions are designated by thesame reference numerals as in FIG. 11, and the description thereof isomitted here. The present embodiment 13 differs from the embodiment 12in that the variable length decoder 311 produces the motion vectorinformation 233 besides the quantization indices 226, and that thecoefficient deletion/addition/correction portion 321 carries out therevision such as the increase or decrease, or correction of thetransform coefficients 227 by using the motion vector information 233besides the image sizes to be transformed which are defined by theinformation 223 commanding the transform.

[0163] Next, the operation will be described.

[0164] In the image coded data analyzer 310 as shown in FIG. 12, thevariable length decoder 311 decodes the first image coded data 220,supplies the inverse quantizer 312 with the resultant quantizationindices 226, and supplies the image coded data synthesizer 320 with themotion vector information 233 which is obtained in the course of thedecoding. The inverse quantizer 312 performs the inverse quantization ofthe quantization indices 226, and transfers the resultant transformcoefficients 227 to the image coded data synthesizer 320 as the codeddata after signal processing 221. In the image coded data synthesizer320, on the other hand, the coefficient deletion/addition/correctionportion 321 receives the inversely quantized transform coefficients 227and motion vector information 233, together with the information 223which commands the transform and defines the image sizes to betransformed. The coefficient deletion/addition/correction portion 321corrects the dimension of the motion vectors in accordance with theratio of the image sizes defined by the information 223 commanding thetransform. Thus changing the dimension of the motion vectors inaccordance with the transform ratio of the image sizes makes it possibleto utilize the vectors used before the transform in substantially thesame form. Accordingly, retrieval of the motion vectors based on thecalculated vectors can improve the retrieval efficiency as compared withoriginal retrieval.

[0165] Thus, according to the embodiment 13, since the motion vectorsare corrected in accordance with the ratio of image sizes to betransformed, the search efficiency can be improved of the motion vectorsin the image coded data after the transform. As a result, the motioncompensative search in a narrower range based on the corrected motionvectors can offer a characteristic nearly equivalent to that obtainedwhen the motion compensative search is carried out in a wider range.

[0166] Embodiment 14

[0167]FIG. 13 is a block diagram showing the internal configuration ofthe image coded data analyzer 310 and image coded data synthesizer 320of an embodiment 14 of the image coded data re-encoding apparatus 30 inaccordance with the present invention, which transforms the sequence ofimages between the first image coded data 220 and the second image codeddata 240, in which like portions are designated by the same referencenumerals as in FIG. 12, and the description thereof is omitted here. Inthe present embodiment 14, the sequence of the images to be transformedis defined by the information 223 commanding the transform.

[0168] In the image coded data analyzer 310 in FIG. 13, the referencenumeral 313 designates an inverse transformer that carries out inversetransform of the inversely quantized transform coefficients 227 outputfrom the inverse quantizer 312 by applying the inverse DCT operation orthe like to the transform coefficients 227, and 314 designates an adderfor adding the processing result of the inverse transformer 313 to thatof the motion compensator which will be described later. The referencenumeral 234 designates a decoded image output from 10 the adder 314 asthe coded data after signal processing 221, and 315 designates a framememory in which the decoded image 234 is stored temporarily. Thereference numeral 316 designates the motion compensator which appliesthe motion compensation to the decoded image one cycle before, which isread out of the frame memory 315, on the basis of the motion vectors 233generated in the decoding process by the variable length decoder 311,and supplies the processing result to the adder 314.

[0169] In the image coded data synthesizer 320, the reference numeral325 designates an inverse quantizer for carrying out inversequantization of the quantization indices 229 output from the quantizer322, 326 designates an inverse transformer for performing the inversetransform of the output of the inverse quantizer 325 by applying theinverse DCT or the like to this output, and 327 designates an adder foradding the processing result of the inverse transformer 326 to a frameimage output from a motion searcher which will be described later. Thereference numeral 328 designates a frame memory which stores the outputof the adder 327 temporarily, and 329 designates a motion searcher. Themotion searcher 329, receiving the image data one cycle before which isread out of the frame memory 328, the motion vector information 233 fromthe image coded data analyzer 310, the decoded image 234 as the codeddata after signal processing 221, and the signal 223 which commands thetransform and defines the sequence and information of the images to betransformed, estimates the dimension of the motion vectors extracted inresponse to the sequence information of the images to be transformed,and carries out the motion search on the basis of the estimation result.The reference numeral 235 designates frame images delivered from themotion searcher 329 to the adder 327 and a subtracter 330 forcalculating the difference between the decoded image 234 which issupplied from the image coded data analyzer 310 as the coded data aftersignal processing 221 and the image data 235 output from the motionsearcher 329. The reference numeral 331 designates a transformer forapplying the transform processing such as DCT operation or the like tothe output of the subtracter 330, and for supplying the processingresult to the quantizer 322.

[0170] Next, the operation will be described.

[0171] Let us assume that the sequences are transformed of the imagesignals included in the first image coded data 220 which is input to theimage coded data analyzer 310 and in the second image coded data 240which is output from the image coded data synthesizer 320, and that thecoding processor 40 which generates the first image coded data 220 andthe decoding processor 50 which decodes the second image coded data 240carry out processing based on transform coding including the motioncompensative prediction, transform and quantization as shown in FIGS. 2and 4, respectively. In this case, the image coded data analyzer 310extracts the motion vectors used in the motion compensation, and themotion searcher 329 estimates the S dimension of the motion vectors inresponse to the sequence information of the images to be transformed.Performing such a search based on the estimated motion vectors whentransforming the picture type to be coded, for example, enables themotion search in a narrower range involving a large volume ofcalculations to keep efficiency equivalent to that of the motioncompensative search in a wider range.

[0172] In the image coded data analyzer 310 as shown in FIG. 13, thevariable length decoder 311 decodes the first image coded data 220, andsupplies the resultant quantization indices 226 to the inverse quantizer312, and the motion vector information 233 obtained in the decodingprocess to the image coded data synthesizer 320 and the motioncompensator 316. The inverse quantizer 312 inversely quantizes thequantization indices 226, and the inverse transformer 313 applies theinverse transform such as inverse DCT operation to the resultanttransform coefficients 227 to supply its result to the adder 314. On theother hand, the motion compensator 316 carries out the motioncompensation of the decoded image one cycle before which is output fromthe frame memory 315 in accordance with the motion vector information233 fed from the variable length decoder 311, and provides the result tothe adder 314. The adder 314 adds the frame images fed from the inversetransformer 313 and the motion compensator 316 to generate the decodedimage 234, and supplies it to the image coded data synthesizer 320 asthe coded data after signal processing 221. Thus, the image coded dataanalyzer 310 not only performs equivalent operation to the decoding by acommon transform coding system with a motion compensation, but alsosupplies the image coded data synthesizer 320 with the decoded image 234as the coded data after signal processing 221 and the motion vectorinformation 233 extracted by the variable length decoder 311.

[0173] In the image coded data synthesizer 320, on the other hand, themotion searcher 329 receives the decoded image 234 and the motion vectorinformation 233, together with the information 223 which commands thetransform and defines the sequence information of the images to betransformed. The motion searcher 329 also receives the image data onecycle before which is read out of the frame memory 328. This image datais generated by inversely quantizing in the inverse quantizer 325 thequantization indices 229 output from the quantizer 322, by applying theinverse transform such as the inverse DCT to the output of the inversequantizer 325 in the inverse transformer 326, by adding by the adder 327the processing results in the inverse transformer 326 and the motionsearcher 329, and by storing the addition result. The motion searcher329 not only generates the frame images 235 on the basis of these datato achieve operation equivalent to that of the common transform codingsystem with motion compensation, but also estimates the motion vectorsof the current coded data by using the motion vector information 233 fedfrom the image coded data analyzer 310, and the sequence informationabout the images to be transformed, which is defined by the information223 commanding the transform, thereby carrying out the motion searchbased on the estimation result. The frame image 235 output from themotion searcher 329 is supplied to the subtracter 330 which calculatesthe difference between the frame image 235 and the decoded image 234delivered from the image coded data analyzer 310 as the coded data aftersignal processing 221. Then, the transformer 331 transforms the outputof the subtracter 330 by applying the DCT operation thereto. Thequantizer 322 performs the quantization, and the variable length coder323 carries out coding of the resultant transform coefficients to thesecond image coded data 240. Thus, the image coded data synthesizer 320not only performs equivalent operation to the coding in the commontransform coding system with the motion compensation by inputting thedecoded image 234 and motion vector information 233 from the image codeddata analyzer 310, but also estimates in the motion searcher 329 thedimension of the motion vectors extracted in the image coded dataanalyzer 310 in response to the sequence information of the images to bechanged which is provided by the information 223 commanding thetransform, thereby performing the motion search based on the estimationresult.

[0174] Thus, according to the embodiment 14, the delay involved incoding is shortened by performing transform which changes the sequenceof the images at reproduction and that of the images after thetransform. Furthermore, it can improve the efficiency of coding usingthe transformed motion vectors by estimating the dimension of the motionvectors in response to the sequence information about the images to betransformed in the processing for changing the sequence of the images tobe transformed.

[0175] Embodiment 15

[0176]FIG. 14 is a block diagram showing the internal configuration ofthe image coded data analyzer 310 and image coded data synthesizer 320of an embodiment 15 of the image coded data re-encoding apparatus 30 inaccordance with the present invention, which transforms the number offrames of the image signal included in the first image coded data 220and that of the image signal included in the second image coded data240, in which the like portions are designated by the same referencenumerals as in FIG. 8, and the description thereof is omitted here. Thepresent embodiment 15 differs from the embodiment 8 in that theinformation 223 commanding the transform defines the frame rate of theimages, and that the coefficient deletion/addition/correction portion321 deletes or corrects the transform coefficients 227, which areinversely quantized by the inverse quantizer 312, by using the framerate information of the images based on the information 223 commandingthe transform.

[0177] Next, the operation will be described.

[0178] Let us assume that the transform is carried out between the firstimage coded data 220 and the second image coded data 240, and that thenumber of frames associated with the first image coded data 220 differfrom that associated with the second image coded data 240, in which eachnumber of frames is defined as that of the decoded image signal per unittime when the first image coded data 220 input to the image coded dataanalyzer 310 and the second image coded data 240 output from the imagecoded data synthesizer 320 are decoded into images. When an image codingmode, which is used as information extracted from the first image codeddata 220, indicates the image which will not be used for future codingof images, the data of the image is deleted. This enables the transformof the frame rate to be achieved without having substantial effect onthe quality of the future images.

[0179] In the image coded data analyzer 310 as shown in FIG. 14, thevariable length decoder 311 decodes the first image coded data 220, andsupplies the inverse quantizer 312 with the resultant quantizationindices 226, and the image coded data synthesizer 320 with the codedpicture information 230 which is obtained in the course of decoding. Theinverse quantizer 312 carries out the inverse quantization of thequantization indices 226, and sends the resultant transform coefficients227 to the image coded data synthesizer 320 as the coded data aftersignal processing 221. In the image coded data synthesizer 320, on theother hand, the coefficient deletion/addition/correction portion 321receives the inversely quantized transform coefficients 227 and thecoded picture information 230 together with the information 223 whichcommands the transform and defines the image frame rate, and decideswhether or not these input data indicate the coded picture which willnot be used for the prediction in the future coding. If so, the data ofthe picture is deleted by applying the method of the embodiment 8,thereby achieving the transform of the frame rate equivalently.

[0180] Thus, according to the embodiment 15, an advantage is gained thatthe transform is readily achieved between the television signals ofdifferent systems by varying the number of frames between the imagesignal included in the first image coded data 220 before the transformand that included in the second image coded data 240 after thetransform.

[0181] Embodiment 16

[0182]FIG. 15 is a block diagram showing the internal configuration ofthe image coded data analyzer 310 and image coded data synthesizer 320of an embodiment 16 of the image coded data re-encoding apparatus 30 inaccordance with the present invention, which estimates the quantizationparameters from the decoded images of the first image coded data 220,and used them for the quantization for generating the second image codeddata 240, in which the like portions are designated by the samereference numerals as in FIG. 13, and the description thereof is omittedhere. In this figure, the reference numeral 236 designates a decodedimage the inverse transformer 313 decodes by applying the inverse DCToperation to the transform coefficients 227 output from the inversequantizer 312. The decoded image 236 is sent to the image coded datasynthesizer 320 as the coded data after signal processing 221. Thereference numeral 332 designates a quantization estimator whichestimates the quantization parameters during the generation of the firstimage coded data 220 from the decoded image 236 fed as the coded dataafter signal processing 221, 237 designates the quantization parameterinformation supplied from the quantization estimator 332 to thequantizer 322, and 238 designates the transform coefficients thetransformer 331 generates from the decoded image 236.

[0183] Next, the operation will be described.

[0184] When transforming the rate of images between the first imagecoded data 220 and the second image coded data 240, the image coded dataanalyzer 310 extracts from the first image coded data 220 thequantization parameters in the quantization process, and the image codeddata synthesizer 320 carries out the quantization using the quantizationparameters. This means that the image coded data analyzer 310 performsthe decoding and the image coded data synthesizer 320 carries out thecoding. This makes it possible to achieve the highest quality transformwhen the bit rate and the coding system are each identical before andafter the transform. In addition, even if the bit rates differ, optimumtransform can be achieved by controlling the quantization parameters inaccordance with the ratio of the bit rates.

[0185] In the image coded data analyzer 310 as shown in FIG. 15, thevariable length decoder 311 carries out the variable length decoding ofthe first image coded data 220 to generate the quantization indices 226,and the inverse quantizer 312 inversely quantizes them to generate thetransform coefficients 227. The inverse transformer 313 applies theinverse DCT operation to the transform coefficients 227 to generate thedecoded image 236, and transfers it to the image coded data synthesizer320 as the coded data after signal processing 221. Thus, the image codeddata analyzer 310 performs operation equivalent to common decoding,thereby outputting the decoded image 236 as the coded data after signalprocessing 221. In the image coded data synthesizer 320, on the otherhand, the transformer 331 receives the decoded image 236 sent as thecoded data after signal processing 221, and applies the DCT operation toit to generate the transform coefficients 238 which are input to thequantizer 322. The quantization estimator 332 also receives the decodedimage 236, estimates the quantization parameters during the generationof the first image coded data 220, and supplies the resultantquantization parameter information 237 to the quantizer 322. Thequantizer 322 quantizes the transform coefficients 238 fed from thetransformer 331 in response to the quantization parameter information237 from the quantization estimator 332. Then, the variable length coder323 carries out coding of the quantization indices 229 to generate andoutput the second image coded data 240.

[0186] Thus, according to the embodiment 16, estimating the quantizationparameters from the decoded image 236 enables the image qualityassociated with the newly generated second image coded data 240 to beimproved, thereby offering an advantage of keeping the image qualityafter the transform in relay transmission. In particular, when the ratesbefore and after the transform are identical, using the estimatedquantization parameters enable the image quality to be kept even afterrepeating a plurality of coding operations. In addition, even if therates are different before and after the transform, an advantage isgained that optimum transform can be achieved by controlling thequantization parameters in accordance with the ratio of the rates.

[0187] Embodiment 17

[0188] The foregoing embodiments can offer configuration not only forforming communication images, but also for multi-site image transformsystems, or systems for copying image data in storage media.

[0189] Furthermore, although the portions playing a major role in thetransform, such as the coefficient deletion/addition/correction portion321, coding parameter correction/transform portion 324 and quantizationestimator 332 are placed in the image coded data synthesizer 320, it isnot necessary that they are provided in the image coded data synthesizer320. For example, they may be placed in the image coded data analyzer310 or in outside independently.

What is claimed is:
 1. An image coded data re-encoding apparatus whichreceives a first image coded data generated by a coding processorperforming coding of a digital input image signal, and which generates asecond image coded data by performing a digital signal processing onsaid first image coded data, said image coded data re-encoding apparatuscomprising: an image coded data analyzer for generating coded data aftersignal processing by performing a first digital signal processing onsaid first image coded data; and an image coded data synthesizer forgenerating said second image coded data by performing on said coded dataafter signal processing a second digital signal processing based onmultiple signals associated with said first image coded data by usingsaid coded data after signal processing output from said image codeddata analyzer and said multiple signals.
 2. The image coded datare-encoding apparatus as claimed in claim 1, wherein said image codeddata analyzer extracts said multiple signals in the course of generatingsaid coded data after signal processing by performing said first digitalsignal processing on said first image coded data, and said image codeddata synthesizer generates said second image coded data by performingsaid second digital signal processing on said coded data after signalprocessing based on said multiple signals by using said coded data aftersignal processing and said multiple signals which are output from saidimage coded data analyzer.
 3. The image coded data re-encoding apparatusas claimed in claim 1, wherein said image coded data re-encodingapparatus further comprises a separator for separating from said firstimage coded data said multiple signals which have been externallycombined with said first image coded data and cannot be extracted fromsaid first image coded data in said first digital signal processing forgenerating said coded data after signal processing, and said image codeddata synthesizer generates said second image coded data by performing onsaid coded data after signal processing said second digital signalprocessing based on said multiple signals by using said coded data aftersignal processing output from said image coded data analyzer and saidmultiple signals output from said separator.
 4. The image coded datare-encoding apparatus as claimed in claim 1, wherein said image codeddata analyzer decodes said first image coded data by performing saidfirst digital signal processing on said first image coded data togenerate decoded image data as said coded data after signal processing,said image coded data re-encoding apparatus further comprises aninformation extractor/estimator for extracting or estimating saidmultiple signals needed for said second digital signal processing fromsaid coded data after signal processing generated by said image codeddata analyzer, and said image coded data synthesizer generates saidsecond image coded data by performing on said coded data after signalprocessing said second digital signal processing based on said multiplesignals by using said coded data after signal processing output fromsaid image coded data analyzer and said multiple signals output fromsaid information extractor/estimator.
 5. The image coded datare-encoding apparatus as claimed in any one of claims 1-4, wherein saidimage coded data synthesizer generates said second image coded data witha data amount different from a data amount of said first image codeddata input to said image coded data analyzer, when said image coded datasynthesizer generates said second image coded data by performing saidsecond digital signal processing on said coded data after signalprocessing from said image coded data analyzer in response to saidmultiple signals from said image coded data analyzer.
 6. The image codeddata re-encoding apparatus as claimed in claim 5, wherein said imagecoded data analyzer extracts transform coefficients or quantizationindices, which are inversely quantized, and wherein said image codeddata re-encoding apparatus further comprises a coefficientdeletion/addition/correction portion for deleting part of said transformcoefficients or quantization indices, which are extracted by said imagecoded data analyzer, and for correcting said transform coefficients orquantization indices in accordance with a ratio of amounts of data to betransformed.
 7. The image coded data re-encoding apparatus as claimed inclaim 5, wherein said image coded data analyzer extracts transformcoefficients or quantization indices, which are inversely quantized, andwherein said image coded data re-encoding apparatus further comprises acoefficient deletion/addition/correction portion for deleting part ofsaid transform coefficients or quantization indices, which are extractedby said image coded data analyzer, and are weighted in accordance withrelationships between said transform coefficients or quantizationindices and their neighboring transform coefficients or quantizationindices.
 8. The image coded data re-encoding apparatus as claimed inclaim 5, wherein said image coded data analyzer extracts transformcoefficients or quantization indices, which are inversely quantized, andwherein said image coded data re-encoding apparatus further comprises acoefficient deletion/addition/correction portion for adding, to saidtransform coefficients or quantization indices which are extracted bysaid image coded data analyzer, new transform coefficients orquantization indices after correcting said new transform coefficients orquantization indices in accordance with a ratio of amounts of data to betransformed.
 9. The image coded data re-encoding apparatus as claimed inclaim 5, wherein said image coded data analyzer extracts transformcoefficients or quantization indices, which are inversely quantized, andwherein said image coded data re-encoding apparatus further comprises acoefficient deletion/addition/correction portion for adding, to saidtransform coefficients or quantization indices which are extracted bysaid image coded data analyzer, new transform coefficients orquantization indices after predicting transform coefficients orquantization indices including said new transform coefficients orquantization indices and their neighboring transform coefficients orquantization indices.
 10. The image coded data re-encoding apparatus asclaimed in claim 5, wherein said image coded data analyzer extractstransform coefficients or quantization indices, which are inverselyquantized, and generates a coding parameter designating a picture typeof a current image to be processed, and wherein said image coded datare-encoding apparatus further comprises a coefficientdeletion/addition/correction portion for increasing a ratio of deletionof said transform coefficients or quantization indices, which areextracted by said image coded data analyzer, if said coding parameterdesignating the picture type indicates, when decision is made whether ornot said current image to be processed is used for prediction in futurecoding, that said picture type is not used for the prediction in thefuture coding.
 11. The image coded data re-encoding apparatus as claimedin claim 5, wherein said image coded data analyzer extracts transformcoefficients or quantization indices, which are inversely quantized, andgenerates a coding parameter designating a picture type of a currentimage to be processed, and wherein said image coded data re-encodingapparatus further comprises a coefficient deletion/addition/correctionportion for decreasing a ratio of deletion of said transformcoefficients or quantization indices, which are extracted by said imagecoded data analyzer, if said coding parameter designating the picturetype indicates, when decision is made whether or not said current imageto be processed is used for prediction in future coding, that saidpicture type is used for the prediction in the future coding.
 12. Theimage coded data re-encoding apparatus as claimed in claim 5, whereinsaid image coded data analyzer extracts transform coefficients orquantization indices, which are inversely quantized, and generates acoding parameter designating a picture type of a current image to beprocessed, and a coding parameter designating a predictive type of animage block of the current image, and wherein said image coded datare-encoding apparatus further comprises a coefficientdeletion/addition/correction portion for increasing a ratio of deletionof said transform coefficients or quantization indices, which areextracted by said image coded data analyzer, if said coding parameterdesignating the predictive type of said image block indicates, whendecision is made whether a current image to be processed is used forprediction in future coding by using the coding parameters generated bysaid image coded data analyzer, that said image block is not used forthe prediction in the future coding, even if said coding parameterdesignating the picture type indicates that the picture type is used forthe prediction in the future coding.
 13. The image coded datare-encoding apparatus as claimed in any one of claims 1-4, wherein saidimage coded data synthesizer generates said second image coded datawhose decoding procedure differs from a decoding procedure of said firstimage coded data input to said image coded data analyzer, when saidimage coded data synthesizer generates said second image coded data byperforming said second digital signal processing on said coded dataafter signal processing from said image coded data analyzer in responseto said multiple signals from said image coded data analyzer.
 14. Theimage coded data re-encoding apparatus as claimed in claim 13, whereinsaid image coded data analyzer extracts from said first image coded datavarious types of coding parameters with an expression form in saiddecoding procedure of said first image coded data, and said image codeddata re-encoding apparatus further comprises a coding parametercorrector/transformer for correcting and transforming said expressionform of said various types of coding parameters, which are extracted bysaid image coded data analyzer, from said expression form in saiddecoding procedure of said first image coded data to an expression formin the decoding procedure of said second image coded data.
 15. The imagecoded data re-encoding apparatus as claimed in any one of claims 1-4,wherein said image coded data synthesizer generates said second imagecoded data including an image signal whose image size differs in time orspace from an image size of an image signal included in said first imagecoded data input to said image coded data analyzer, when said imagecoded data synthesizer generates said second image coded data byperforming said second digital signal processing on said coded dataafter signal processing from said image coded data analyzer in responseto said multiple signals from said image coded data analyzer.
 16. Theimage coded data re-encoding apparatus as claimed in claim 15, whereinsaid image coded data analyzer extracts transform coefficients orquantization indices, which are inversely quantized, and wherein saidimage coded data re-encoding apparatus further comprises a coefficientdeletion/addition/correction portion for changing an amount of saidtransform coefficients or quantization indices extracted by said imagecoded data analyzer, and for correcting said transform coefficients orquantization indices, which are extracted by said image coded dataanalyzer, in accordance with a ratio of the image sizes to betransformed.
 17. The image coded data re-encoding apparatus as claimedin claim 15, wherein said image coded data analyzer extracts motionvectors used for motion compensation, and wherein said image coded datare-encoding apparatus further comprises a coefficientdeletion/addition/correction portion for correcting dimension of saidmotion vectors extracted by said image coded data analyzer in accordancewith a ratio of the image sizes to be transformed.
 18. The image codeddata re-encoding apparatus as claimed in any one of claims 1-4, whereinsaid image coded data synthesizer generates said second image coded dataincluding an image signal whose sequence differs from a sequence of animage signal included in said first image coded data input to said imagecoded data analyzer, when said image coded data synthesizer generatessaid second image coded data by performing said second digital signalprocessing on said coded data after signal processing from said imagecoded data analyzer in response to said multiple signals from said imagecoded data analyzer.
 19. The image coded data re-encoding apparatus asclaimed in claim 18, wherein said image coded data analyzer extractsmotion vectors used for motion compensation, and wherein said imagecoded data re-encoding apparatus further comprises a motion searcher forestimating dimension of said motion vectors extracted by said imagecoded data analyzer in accordance with said sequence of the imagesignals to be transformed.
 20. The image coded data re-encodingapparatus as claimed in any one of claims 1-4, wherein said image codeddata synthesizer generates said second image coded data whose decodedimage signal includes a number of frames per unit time different from anumber of frames per unit time of a decoded image signal of said firstimage coded data input to said image coded data analyzer, when saidimage coded data synthesizer generates said second image coded data byperforming said second digital signal processing on said coded dataafter signal processing from said image coded data analyzer in responseto said multiple signals from said image coded data analyzer.
 21. Theimage coded data re-encoding apparatus as claimed in claim 5, whereinsaid image coded data analyzer generates as the coded data after signalprocessing a decoded image obtained by decoding said first image codeddata, wherein said image coded data re-encoding apparatus furthercomprises a quantization estimator for estimating, from said decodedimage output from said image coded data analyzer, quantizationparameters obtained in the course of generating said first image codeddata, and wherein said image coded data synthesizer generates saidsecond image coded data by using said quantization parameters estimatedby said quantization estimator.